Preparation of small silicon carbide quantum dots by wet chemical etching
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Zsolt Szekrényes and István Balogh Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, H-1525 Budapest, Hungary
Zsolt Czigány Institute for Technical Physics and Materials Science, Research Centre of Natural Sciences, Hungarian Academy of Sciences, H-1525 Budapest, Hungary
Katalin Kamarás Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, H-1525 Budapest, Hungary
Adam Gali Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, H-1525 Budapest, Hungary; and Department of Atomic Physics, Budapest University of Technology and Economics, H-1111 Budapest, Hungary (Received 30 March 2012; accepted 14 June 2012)
Fabrication of nanosized silicon carbide (SiC) crystals is a crucial step in many biomedical applications. Here we report an effective fabrication method of SiC nanocrystals based on simple electroless wet chemical etching of crystalline cubic SiC. Comparing an open reaction system with a closed reaction chamber, we found that the latter produces smaller nanoparticles (less than 8 nm diameter) with higher yield. Our samples show strong violet-blue emission in the 410–450 nm region depending on the solvents used and the size. Infrared measurements unraveled that the surface of the fabricated nanoparticles is rich in oxidized carbon. This may open an opportunity to use standard chemistry methods for further biological functionalization of such nanoparticles.
I. INTRODUCTION
The search for ideal in vivo luminescent biomarkers is a great challenge because there are stringent criteria to be fulfilled: the biomarkers should (i) be nontoxic and bioinert, (ii) be photostable, i.e., be nonbleaching, (iii) show no intermittency in luminescence, i.e., there should be no blinking, (iv) be small where the critical diameter is close to 6 nm, (v) be producible in large amounts for biological studies. Organic dye molecules are well characterized and can be synthesized in large selection of excitation and emission wavelength range. Dye molecules fulfill criteria (iv)–(v) but they often bleach and are toxic because the visible emission comes from double bonds or aromatic bonds.1 Recently, small luminescent nanocrystals have been synthesized that are photostable. The most successful candidate out of above is a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2012.223 44
J. Mater. Res., Vol. 28, No. 1, Jan 14, 2013
http://journals.cambridge.org
Downloaded: 28 Apr 2015
cadmium selenide (CdSe) where the size of the particles could be well controlled. Depending on the size, CdSe nanocrystals emit light of various wavelengths due to quantum confinement of the host electron states, so they are called CdSe quantum dots (QDs).2 CdSe and other compound semiconductor QDs contain heavy metals that are toxic.3 While the diameter of these QDs is in the range of 1–5 nm, a protecting shell is needed to avoid toxicity
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